KR20140073576A - Coating compositions for inorganic casting molds and cores, containing salts, and use thereof - Google Patents

Abstract

The subject of the present invention is a sizing composition as a coating material for a casting mold. The sizing composition is suitable for casting cores and casting molds, in particular for casting cores and casting molds made using water glass as binder. The sizing composition comprises a specific salt.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a coating composition for inorganic casting molds and casting cores containing a salt,

The present invention relates to a sizing composition as a coating material for a casting mold. The sizing composition is suitable for casting cores and casting molds, in particular for the casting cores and casting moldings made using water glass as binder. The sizing composition comprises a particular salt.

Casting molds can be obtained from refractory materials, such as sand, and are produced by casting into a casting mold and combining with a suitable binder to ensure sufficient mechanical strength of the casting mold. Refractory casting mold materials and suitable binders are used to make the casting molds. Since the refractory casting mold material is preferably provided in a free-flowing form, the casting mold material can be filled into a suitable hollow mold and concentrated. Because of the solid agglomeration between the particles of the casting mold material through the binder, the casting mold achieves the necessary mechanical stability.

An inorganic binder as well as an organic binder may be used to prepare the casting mold, and the curing of the binder may be performed by a cold process or a hot process. The low-temperature method generally refers to a method wherein the casting mold is not heated but is carried out at room temperature. At this time, the curing is carried out mostly through a chemical reaction, which is caused, for example, as a catalyst, by passing the gas through a mold to be cured. In the case of the high temperature process, after molding, the mold mixture is heated to a sufficiently high temperature, for example to discharge the solvent present in the binder or to initiate a chemical reaction, And cured by cross-linking.

Regardless of the curing mechanism, what is common to all organic systems is that when the liquid metal fills the casting mold, the organic system is thermally decomposed and the benzene, toluene, xylene, phenol, formaldehyde, such as cracking products.

Various measures have been taken to minimize these emissions, but in the case of organic binder, the emissions could not be completely suppressed. In order to minimize or suppress the emission of decomposition products during the casting process, a binder based on inorganic materials or a binder containing a very low proportion of organic compounds may be used. Such binder systems have long been known for a long time.

A binder system has been developed which can be cured through gas inflow. Such a system is described, for example, in GB 782205 in which alkali water glass is used as the binder and the binder can be cured through the inflow of CO ₂ . US 6972059 B1 discloses an exothermic feeder mass comprising an alkali silicate as a binder. In addition, binder systems have been developed that can be self-cured at room temperature. Such systems based on phosphoric and metal oxides are described, for example, in US 5,582,232. Finally, inorganic binder systems are known, and the system is cured at elevated temperatures, such as hot tools. Such heat-curing binder systems are known, for example, from US 5,474,606, which discloses a binder system comprised of alkali water glass and silica silica.

US 7022178 B1 discloses a binder system for cast sand for making casting cores. The binder system of the waterglass series consists of an aqueous alkali silicate solution and a hygroscopic base added in a ratio of 1: 4 to 1: 6, for example, sodium hydroxide. The water glass has a SiO ₂ / M ₂ O module of 2.5 to 3.5 and a solids fraction of 20 to 40%. In order to obtain a flexible mold material mixture which can be filled into a cast mold of a complex shape and to control the hygroscopic properties, the binder system comprises a surface active material such as silicone oil having a boiling point > The binder system may be blended with a suitable refractory material, such as silica sand, and then fired into the core box via a core shooting machine. The curing of the mold material mixture is carried out by removing the remaining water. Drying or hardening of the casting mold may be carried out through microwaves.

However, inorganic binding agents have disadvantages when compared to organic binding agents. For example, known inorganic binders cause high stability or low stability of cast molds made using inorganic binders for water. As a result, the storage of the molded product over a long period of time, like the conventional organic binder, can not be guaranteed. In order to obtain high initial strength and better durability against humidity and to obtain better results at the casting surface during casting, US 7770629 B2 proposes a mold material mixture which, together with the refractory casting mold material, Based binders. A fraction of particulate metal oxide is added to the casting material mixture. Preferably, precipitated silica or pyrogenic silica is used as the particulate metal oxide.

In general, a known method for manufacturing casting molds and casting cores involves applying a refractory mold coating, referred to as a sizing agent, to the surface of a mold base that is at least in contact with the cast metal. The casting coating primarily has the purpose of affecting the surface of the forming part and improving the appearance of the casting, metallurgically affecting the casting, and / or preventing casting defects.

Conventionally used sizing agents include, for example, clay, quartz, diatomaceous earth, crystal valleyite, tridimite, aluminum silicate, zirconium silicate, mica, refractory clay and coke and graphite as base materials. This base material is a part of the sizing agent which covers the mold surface and closes the micropores to inhibit the inflow of the casting metal.

Through this coating, the surface of the casting mold can be deformed and can be controlled by the properties of the metal to be processed. For example, the appearance of the casting due to the sizing agent can be improved by the production of a smooth surface, since heterogeneity caused by different particle sizes of the mold material is corrected through the sizing agent. Also, for example, the additive is selectively transferred to the casting through the sizing agent on the casting surface, whereby the sizing agent can metallurgically affect the casting, which improves the surface properties of the casting.

Furthermore, the sizing agent forms a layer that chemically blocks the casting mold from the liquid metal when casting. As a result, adhesion between the casting and the casting mold is suppressed, so that the casting can be easily removed from the casting mold. The sizing agent can also be used to control the reliable heat transfer between the liquid metal and the casting mold, for example to form the microstructure of the specific metal through a cooling rate.

Today, the curing of the inorganic binder used is increased through the condensation reaction initiated by the increase in temperature, wherein the binder bridge formation is carried out through the cleavage of the water. Like many chemical reactions, there is a reversible reaction, that is to say that the bond can be broken up newly by contact with water and water, and the degree of this reversible reaction is considerably reduced in the process parameters for producing the casting cores Respectively. Under the process parameters typically used in mass production (rapid cycling time, high temperature), the casting mold loses its solidity due to contact with water and contact with alcohol in part, The strength becomes weak and the shape of the casting mold can not be maintained.

It is an object of the present invention to provide a sizing agent through which the most error-free coatings, especially mineral casting molds and casting cores, can be ensured and the stability of the casting molds or casting cores, It does not affect.

This object of the invention is solved by a sizing composition having the features of claim 1, the preferred form being the subject of the dependent claims or described in detail below.

The sizing composition according to the invention is provided in the form of a paste or suspension according to a preferred embodiment. In this embodiment, the sizing composition comprises a carrier fluid.

Surprisingly, the addition of certain salts in a specific concentration range to the aqueous sizing composition can result in a sustainable improvement in the quality of the sized mineral casting cores and casting molds, for example the storage stability of the casting molds and casting cores It has been found that it can be achieved without problems.

Surprisingly, it has been found that metal magnesium and / or manganese can be used to solve this problem. Preferably, the manganese salt can be used in the oxidation state +2 or +4. Particularly preferably, the magnesium salt is used in the oxidation state +2 and the manganese salt is used in the oxidation state +2. The concentration of the salt is more than 1% by weight, preferably more than 3% by weight, particularly preferably more than 5% by weight, based on the sizing composition. According to one embodiment, the concentration of the salt is limited by the amount of carrier fluid used and the saturation concentration of the species used in each case. According to another embodiment, the maximum saturation concentration is less than 10% by weight based on the sizing composition. Preferably, a sulfate ion is used as an anion, and / or monovalent chloride ion is particularly preferably used as a counter ion.

For example, depending on the desired use of the sizing composition as a base coating or top coating and the desired layer thickness of the coating made of the sizing composition, other characteristic parameters of the sizing composition may be adjusted .

The ester of formic acid (methanoic acid) is used as an additional additive component of the sizing composition and the average chain length of the alcohol or alcohol mixture used for esterification is in particular less than 6 carbon atoms, preferably less than 3 Carbon atom.

Particularly preferably, formic acid methyl ester (methyl formate) and formic acid ethyl ester (ethyl formate) are used. In addition, all or a part of the alcohol group may have one or two additional groups such as an ether group, a hydroxyl group, an ester group or a carboxyl group, and the formic acid may be condensed, for example, by condensation through a second or third hydroxy group Can be crosslinked.

The total content of the additive is 1 to 8% by weight, preferably 2 to 8% by weight, particularly preferably 3 to 6% by weight based on the sizing composition. As a suitable additive for use, there is "pure methyl formate " which is a product of BASF. The CAS number is 107-31-3.

For example, the sizing agent may comprise a combination of specific clays as a component of the sizing agent. The clay materials used are the following combinations:

a) 1 to 10 parts by weight, especially 1 to 5 parts by weight of palygorskite,

b) from 1 to 10 parts by weight, especially from 1 to 5 parts by weight of hectorite, and

c) from 1 to 20 parts by weight, in particular from 1 to 5 parts by weight of sodium bentonite

(In each case relative to one another), in particular the weight ratio of palygourite to hectorite is from 1: 0.8 to 1.2, the weight ratio of palyurite and hectorite to sodium bentonite is from 1: 0.8 to 1.2. The total clay content of the clay in the sizing agent is from 0.1 to 4.0% by weight, preferably from 0.5 to 3.0% by weight, particularly preferably from 1.0 to 2.0% by weight, based on the solids content of the sizing composition. By using the clay, the storage stability of the casting core and the casting mold can be further improved.

The carrier fluid may be partially or completely formed by water. The carrier fluid is a component that can evaporate at a temperature of 160 ° C and normal pressure, and in this sense the component is not a solid content according to the definition of the present invention. The carrier fluid comprises more than 50% by weight, preferably 75% by weight, particularly preferably 80% by weight and, in some cases, more than 95% by weight of water.

Another component of the carrier fluid may be an organic solvent. Suitable solvents are polyalcohols, alcohols including polyether alcohols. For example, the alcohol is ethanol, n-propanol, isopropanol, butanol, and glycol.

The solids content of the ready-to-use sizing composition is preferably adjusted in the range of from 10 to 85% by weight, or in particular 30 to 70% by weight in the form of sale (before dilution).

The sizing composition according to the present invention comprises a refractory material in the form of one or more powders. This refractory material is used to close the pores in the casting mold for the influx of liquid metal. In addition, thermal insulation between the casting mold and the liquid metal is achieved due to the refractory material. As the refractory material, a refractory material conventionally used in metal casting may be used. Suitable refractory materials include, but are not limited to, quartz, aluminum oxide, zirconium oxide, aluminum silicate such as pyrophyllite, marble, marble, chamois, zirconium sand, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, Kaolin kaolin, kaolin kaolin, aged rock, meta kaolinite, iron oxide and / or bauxite.

The refractory material is provided in powder form. The particle size is chosen so that a stable structure in the coating is produced and the sizing agent can be distributed without problems on the wall of the casting mold, preferably via a spray device. The refractory material preferably has an average particle size (measured through light scattering according to DIN / ISO 13320) in the range of from 0.1 to 500 mu m, particularly preferably in the range of from 1 to 200 mu m. As the refractory material, materials which have a melting point of at least 200 캜 above the liquid metal temperature and which do not react with the metal independently are suitable.

For example, the proportion of refractory materials (each contributing only to solids content) to the solids content of the sizing composition in the form of a compatible paste is preferably greater than 70 wt%, particularly preferably greater than 80 wt% More preferably greater than 85% by weight.

Depending on the embodiment (each contributing only to solids content), the proportion of the refractory material is selected to be less than 70 wt%, according to another embodiment less than 60 wt%, and in yet another embodiment less than 50 wt%.

The sizing agent according to the present invention may include at least a suspending agent according to an embodiment. Since the anti-settling agent acts to increase the stickiness of the sizing agent, the solid component of the sizing agent in the suspension does not sink, or only the finer extent of the sizing agent sinks. In order to increase the tackiness, inorganic materials as well as organic materials or mixtures of such materials may be used. Suitable inorganic anti-settling agents include strong swelling clays such as, for example, sodium bentonite.

Alternatively or additionally, an organic thickener may also be selected as the anti-settling agent, since after the protective coating has been applied, the protective coating releases substantially no water upon contact with the liquid metal This is because the thickener can be dried. As the organic suspending agent, for example, a swellable polymer is suitable, and examples of the swellable polymer include carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose, vegetable slurry, polyvinyl alcohol, polyvinylpyrrolidone Money, pectin, gelatin, agar-agar, polypeptides and / or alginates.

The ratio of the anti-settling agent to the total sizing composition is preferably selected from 0.1 to 5% by weight, particularly preferably 0.5 to 3% by weight, particularly preferably 1 to 2% by weight.

According to a preferred embodiment, the sizing agent according to the invention comprises at least one binder as an additional component. The binder allows the protective coating made of the sizing agent or sizing agent to better adhere to the wall of the casting mold. In addition, the bonding agent increases the mechanical stability of the protective coating, resulting in less erosion under the influence of liquid metal. Preferably, a wear resistant coating is obtained because the binder is cured very reliably irreversibly. In particular, the binder has the advantage that it does not soften again when in contact with atmospheric humidity. All binders used in the sizing agent may be included as such. In addition, inorganic binder as well as organic binder may be used. As binders, for example clays, especially bentonites and / or kaolins, may be used.

 The proportion of the binder is preferably from 0.1 to 20% by weight, particularly preferably from 0.5 to 5% by weight, based on the solids content of the sizing composition.

 According to another preferred embodiment, the sizing agent comprises a graphite ratio. This supports the formation of lamellar carbon at the interface between the casting mold and casting mold. The proportion of graphite is preferably in the range of 1 to 30% by weight, particularly preferably in the range of 5 to 15% by weight based on the solids content of the sizing composition. The graphite has a favorable effect on the surface quality of the castings in cast iron castings.

In some cases, the sizing composition according to the present invention may comprise another conventional component for the sizing agent, such as wetting agents, defoamers, pigments, colorants or biocides. The ratio of these additional components to the ready-to-use coating composition is preferably selected in the range of less than 10% by weight, particularly preferably less than 5% by weight, particularly preferably less than 1% by weight.

As the wetting agent, for example, anionic and non-anionic surfactants having an HSB value of at least 7 can be used. An example of such a wetting agent is disodium dioctylsulfosuccinate. The wetting agent is preferably used in an amount of 0.01 to 1% by weight, particularly preferably 0.05 to 0.3% by weight, based on the sizing composition ready for use.

A defoamer, also referred to as an antifoamer, may be used to inhibit foam formation during the manufacture or application of the sizing composition. When the sizing composition is applied, bubbles may result in non-uniform layer thicknesses and holes in the coating. As the defoaming agent, for example, silicone oil or mineral oil may be used. The antifoaming agent preferably contains an amount of 0.01 to 1% by weight, particularly preferably 0.05 to 0.3% by weight, based on the sizing composition ready for use.

In some cases, conventional pigments and colorants may be used in the sizing composition according to the present invention. Such pigments and colorants are added, for example, to obtain a strong separation effect of the layer from different contrasts or castings of different layers.

Examples of the pigment include red iron oxide, yellow iron oxide and graphite. Examples of such colorants are colorants such as the colorant series Luconyl (R) from BASF AG, Ludwigshafen, DE. The colorant and the pigment preferably contain an amount of 0.01 to 10% by weight, particularly preferably 0.1 to 5% by weight, based on the solid content of the sizing composition.

According to yet another embodiment, the sizing composition comprises a bioside to inhibit bacterial penetration, as well as to inhibit negative effects on rheology and binding ability of the binder. Preferably, this is especially the case where the transport fluid contained in the sizing composition is generally formed to the weight of water, i.e. the sizing composition according to the invention is provided in the form of a so-called aqueous sizing agent. Examples of suitable biocides include formaldehyde, 2-methyl-4-isothiazolin-3-one (MIT), 5-chloro-2-methyl-4-isothiazolin- -Benzisothiazolin-3-one (BIT). Preferably, MIT, BIT or a mixture of the foregoing is used. The bioside is generally used in an amount of 10 to 1000 ppm, preferably 50 to 500 ppm, based on the weight of the sizing composition ready for use.

The sizing composition according to the present invention may further comprise other components conventionally used in sizing agents in addition to the above components.

The sizing composition according to the present invention can be prepared by a conventional method. For example, the sizing composition according to the present invention can be prepared by dispersing the clay provided with water and acting as an anti-settling agent through a high shear stirrer. The refractory component, the pigment, the colorant and the metallic additive are then mixed until a homogeneous mixture is produced. Finally, the wetting agent, defoamer, bioside and binder are mixed.

The sizing composition according to the present invention may be manufactured and sold as a sizing agent in a ready-to-use form. However, the sizing agent according to the present invention may be manufactured and sold in a concentrated form. In this case, the amount of carrier fluid needed to produce the ready-to-use sizing agent is added, and the addition of such a carrier fluid is intended to control the desired tackiness and concentration of the sizing agent. The sizing composition according to the present invention may also be provided and sold in the form of a kit, for example, the solid component (s) and the solvent component (s) are provided side by side in a separate container. The solid component (s) may be provided in a separate vessel as a solid mixture in powder form.

Optionally, other liquid component (s) to be used, such as binders, surfactants, wetting / defoaming agents, pigments, colorants and biocides, may be provided in containers again separated from these kits. The solvent component (s) may, for example, be contained in a single vessel, if desired, for example, or the solvent component may be provided in a separate vessel separated from other optional components. To prepare the ready-to-use sizing agent, the amount of suitable solid components, the amount of another optional component, and the amount of solvent component are mixed with each other.

The sizing composition according to the invention is suitable for coating of cast molds. As used herein, the expression "casting mold" includes all types of solids needed to make a casting, such as casting cores, casting molds and molds. The use of sizing agents according to the present invention may in part also include coating of cast molds. The sizing agent is used for a casting mold for metal working and is obtained from a mixture of mineral mold materials comprising at least one refractory casting mold material, a binder based on water glass, and preferably a proportion of metal oxide, Wherein the metal oxide is selected from the group of silicon, especially amorphous silicon dioxide, aluminum oxide, titanium oxide or zinc oxide, and mixtures thereof, said metal oxide being preferably provided in the form of particles and having a particle size of less than 300 μm . For example, the amorphous silicon dioxide is obtained through a precipitation process starting from a water glass, which can be obtained by solubilizing silica sand or sodium carbonate with potassium carbonate. The SiO ₂ thus produced is named precipitated silica according to the process conditions. Another important modified manufacturing process is the production of so-called pyrogenic SiO ₂ in an oxyhydrogen gas flame starting from liquid chlorosilanes such as silicon tetrachloride. A method of making a casting mold for processing metal using a mixture of a casting material and a cured casting material is known from WO 2006/024540 (= US 7770629 B2), which publication is incorporated herein by reference . A preferred casting mold mixture is the subject of the claims of WO 2006/024540.

The cast molds to be coated generally include:

a) more than 80% by weight of refractory casting mold material (including additives acting like refractory casting mold material),

b) 0.01 to 5% by weight of a cured water glass as the binder, and

c) optionally from 0 to 5% by weight of said metal oxide or metal oxides.

The present invention also relates to a process for the production of a sizing casting mold for metalworking applying a sizing agent to a partially or fully cured mineral mold material mixture as described above. Application or manufacture of the sizing agent may be carried out as follows:

In the case of dipping as a coating method, the casting mold, in which the base coating is applied to the mold cavity of the casting mold as occasion demands, is dipped in the container filled with the sizing composition according to the invention for about 2 seconds to 2 minutes. The casting mold is then separated from the sizing composition and run out of the excess sizing composition of the casting mold. The time required for runout of the excess sizing composition after dipping is dependent on the run out-behavior of the sizing composition used.

In the case of spraying as a coating method, a commercially available pressure vessel spraying apparatus is used. At this time, the sizing composition is filled in the pressure vessel in a diluted state. Due to the adjustable overpressure the sizing agent can be pressurized into a spray gun in which the sizing agent is sprayed through atomizing air which can be controlled separately. During spraying, the preferred conditions are such that the pressure for the sizing composition and fine atomizing air is adjusted in the spray gun so that the sprayed sizing composition is still wet, but evenly applied, in the cast mold or casting mold.

In the case of a flow coating as the application method, the casting mold, optionally coated with a base coat in the mold cavity, is covered with a sizing composition according to the invention via a tube, lance or similar tool. In the process, the casting mold is completely covered with the sizing composition, and the excess sizing composition is run out from the casting mold. The time required for runout of the excess sizing composition after flow coating depends on the runout behavior of the sizing composition used.

In addition, the sizing agent may be applied via painting.

The carrier fluid contained in the sizing agent is then evaporated so that a dried sizing agent layer is obtained. All conventional drying methods are used as drying methods, such as air drying, dehumidifying air drying, microwave or infrared drying, convection oven drying, and the like. In a preferred embodiment of the present invention, the coated casting molds are dried in a convection oven at 20 to 250 캜, preferably 50 to 180 캜.

When using an alcohol based sizing agent, the sizing composition according to the invention is preferably dried by burning off with an alcohol or alcohol mixture. Further, the coated casting mold is further heated through the combustion heat. In another preferred embodiment, the coated casting molds are dried in air or dried using a microwave oven without any further processing.

The sizing agent may be applied in the form of a single layer or in the form of a plurality of layers stacked one on top of the other. Further, the individual sizing agents in the sizing composition may be the same or different. For example, the base coating may first be prepared from commercially available sizing agents, which do not contain the metallic additives according to the invention. As the primer coating, for example, a sizing agent based on water or a sizing agent based on alcohol may be used. It is also possible to produce all the layers with the sizing composition according to the present invention. However, the layer which will later come into contact with the liquid metal is produced from the sizing agent according to the invention. When multiple layers are applied, each individual layer may be completely or partially dried after application.

The coating prepared from the sizing composition has a dried layer thickness of at least 0.1 mm, preferably at least 0.2 mm, particularly preferably at least 0.45 mm, particularly preferably at least 0.55 mm. According to an embodiment, the thickness of the coating is selected to be less than 1.5 mm. The thickness of the dried layer is such that the layer thickness of the dried coating generally corresponds to the layer thickness of the dried coating obtained through complete removal of the solvent component and, if appropriate, subsequent curing. The dried layer thickness of the primer coating and the top coating is preferably determined by measurement by a wet layer thickness comb. The casting mold can then be fully assembled if necessary.

The casting is preferably carried out for the production of iron castings and steel castings.

Example:

In this example, the effect of the sizing agent salt on the rigidity of the sized casting core was tested. Sizes 1 to 3 of the used casting cores have the compositions described in Tables 1 to 3.

Composition of sizing agent Sizing agent  One Sizing agent  2 Sizing agent  3 ingredient weight% weight% weight% water 31 31 31.0 MnCl ₂ 5.0 - - MgSO ₄ - 5.0 0.5 Zircon powder 45 탆 19.5 19.5 21.0 Actigel 208 1.0 1.0 1.0 PVA solution (25%) 1.5 1.5 1.5 Satintone W® 17 17 18 Surfynol® SEF (wetting agent 1) 0.2 0.2 0.2 Dynol (wetting agent 2) 0.05 0.05 0.05 Foamstar® MF342 (antifoaming agent) 0.2 0.2 0.2 Pyrax RG 140 12 12 13 Gloss Graphite powder 85% C 12 12 13 Acticide® F (N) (Preservative 1) 0.4 0.4 0.4 Acticide® MBS (Preservative 2) 0.15 0.15 0.15

Mold casting sizing agents were prepared as follows: Water was provided in a vessel, where the clay was cracked for at least 15 minutes using a high shear unit and a toothed disk.

The refractory component, the pigment and the colorant are then mixed for at least 15 minutes until a homogeneous mixture is produced. Finally, additives such as wetting agent, defoamer and preservative and binder are mixed for 5 minutes.

The sizing agent was adjusted in the range of 0.6 Pas for the following tackiness experiment suitable for application. The adjustment was made by adding a corresponding amount of water to the original composition and subsequent homogenization. The main feature in this case is stickiness, which was measured at 20 ° C by a Brookfield viscometer (DIN EN ISO 2555) and a DIN 4 mm viscosity cup (DIN EN ISO 2431).

Applied parameters Sizing agent  One Sizing agent  2 Sizing agent  3 Brookfield [Pas] 0.6 0.6 0.6 Time [s] 15.5 15.5 15.5 Solid content [%] 57.5 57.5 62.5 Penetration depth [mm] 2 2 2 According to the invention According to the invention Not according to the invention

The manganese chloride contained in sizing agent 1 and the magnesium sulfate contained in sizing agent 2 result in a significant decrease in dissolution and softening of the inorganic binder at the surface when applied to mineral casting cores and casting cores. Thus, the stability of a higher sized sintered core compared to conventional sizing can be observed.

This effect is based on the fact that the water contained in the sizing must absorb the ions generated during the melting process when in contact with the cured inorganic binder. However, if the water contains an abnormally high ion ratio, the solubility product will increase and the absorption of other ions will be prevented or prevented. Accordingly, the dissolved salt of the sizing contributes to preventing destabilization of the mineral casting cores and the casting mold during the sizing process.

Similar behavior can be achieved in the same way by salts of the chemically related metals magnesium and metal manganese.

Manufacturing and testing of mold material specimens

For experimental purposes, the geometry of two different casting cores was investigated. One of these geometries, the so-called Georg Fischer test bar, observes the behavior of the sieved specimen in a thick casting coronal geometry, while other geometries, the so-called long cores, Observe the behavior of the specimen that is sized in the structure. The Georg Fischer test bar is a square shaped test bar having dimensions of 150 mm x 22.36 mm x 22.36 mm. The long casting cores have dimensions of 13 mm x 20 mm x 235 mm.

The composition of the casting material mixture is listed in Table 3. The following procedure was followed to prepare the Georg Fischer test bars: The ingredients listed in Table 3 were mixed in a laboratory paddle vane type mixer (Vogel & Schemmann AG, Hagen, DE).

Silica was provided for this purpose, and water glass was added under stirring. A sodium water glass having a proportion of potassium as the water glass was used. Module SiO ₂ of the water glass: M ₂ O is about 2.2, where M is the sum of sodium and potassium. After the mixture was stirred for 1 minute, amorphous silicon dioxide was optionally added under stirring. The amorphous silicon dioxide is a pyrogenic silica from RW Silicium. The mixture was then stirred for another 1 minute.

The mold material mixture was transferred to a storage bunker via a H 2.5 hot-box core shooting machine from Roeperwerk-Giessereimaschinen GmbH, Viersen, DE, Lt; 0 > C. The mold material mixture was introduced into the forming tool using compressed air (5 bar) and placed in a forming tool for an additional 35 seconds. To accelerate curing of the mixture, hot air (2 bar, 150 캜 when entering the tool) was guided past the forming tool during the last 20 seconds. The forming tool was opened, and the test bar was separated.

The coating composition was applied to the test bars via dipping, and the application parameters are listed in Table 2. The test bars were coated immediately after being separated from the forming tool or after being cooled for 30 minutes.

The coated test bars were coated with a coating and then held in a drying oven at 150 < 0 > C for 30 minutes.

To determine the bending strength, the test bar was inserted into a Georg Fischer strength testing device with a three-point bending device (DISA Industrie AG, Schaffhausen, CH) and the force causing the test bar to break was measured.

The bending strength of the uncoated test bars was measured as follows:

- 10 seconds after separation (high temperature strength)

- 1 hour (low temperature intensity) after separation.

The test bars were coated as follows:

- Coating (high temperature strength) for 1 minute after being separated.

- Coated for 30 minutes after separation (low temperature strength).

The bending strength of the coated test bars was measured as follows:

- 10 seconds after separation from the drying oven (high temperature strength, high temperature coating)

- Coating (low temperature strength, hot coating, immediately after being removed from the oven) for 30 minutes after being separated,

- 10 seconds after separation from the drying oven (high temperature strength, low temperature coating, room temperature 20 ° C)

- Coating (low temperature strength, low temperature coating) for 30 minutes after being separated.

Composition of the mold material mixture Silica H32 Alkali-water glass Amorphous silicon dioxide coating One 100 GT 2.0 0.5 - Comparison, not according to the invention 2 100 GT 2.0 0.5 Sizing first According to the invention 3 100 GT 2.0 0.5 Sizing No.2 According to the invention 4 100 GT 2.0 0.5 Sizing third Not according to the invention

Strength of Georg Fischer test bars High temperature strength, high temperature coating [N / cm ² ] Low temperature strength, high temperature coating [N / cm ² ] High temperature strength, low temperature coating [N / cm ² ] Low temperature strength, low temperature coating [N / cm ² ] One 400 450 400 450 Comparison, not according to the invention 2 290 390 330 460 According to the invention 3 290 350 300 450 According to the invention 4 220 - (destroyed) - (destroyed) 300 Not according to the invention

Strength of Long Casting Core High temperature strength, high temperature coating [N / cm ² ] Low temperature strength, high temperature coating [N / cm ² ] High temperature strength, low temperature coating [N / cm ² ] Low temperature strength, low temperature coating [N / cm ² ] One 250 280 250 280 Comparison, not according to the invention 2 220 240 270 270 According to the invention 3 200 250 260 250 According to the invention 4 - (destroyed) - (destroyed) - (destroyed) - (destroyed) Not according to the invention

The use of alcohol-containing coatings is undesirable because of the disadvantages of producing emissions during the casting process. Standardized coatings based on water Tests made up of mold materials containing waterglass lose much of their strength when used (Sizing 4).

Surprisingly, it has been found that the addition of certain salts in a certain concentration range can improve the quality of the sized inorganic casting mold and the casting mold while finding the possibility to inhibit the reaction between the water from the coating and the binder of the mold material, It has been found that the storage stability of the casting mold and the casting mold can be achieved without any problem for several days. Metal magnesium or metal manganese may be used for this purpose. Preferably, a manganese salt having a valence of +4 is used. Particularly preferably, magnesium having a valence of +2 and manganese having a valence of +2 are used.

Preferably, the sulfate ion is used as the anion, and particularly preferably the monovalent chloride ion is used as the anion.

The concentration of the salt is in particular in the range between 1% by weight and the respective saturated concentration, preferably 3% by weight and the respective saturated concentration, particularly preferably between 5% by weight and the respective saturated concentration.

Claims (15)

A sizing composition comprising:
(A) a salt of metal magnesium and / or metal manganese which can be combined in a concentration of greater than 1% by weight relative to the sizing composition;
(B) a carrier fluid comprising or consisting of water; And
(C) Refractory materials. The method according to claim 1,
Wherein a sulfate ion and / or a chloride ion is used as an anion. 3. The method according to claim 1 or 2,
Manganese is used in oxidation state +2 or +4, and / or magnesium is used in oxidation state +2. 4. The method according to any one of claims 1 to 3,
Wherein the concentration of the salt is greater than 3 wt%, especially greater than 5 wt%, based on the sizing composition. 5. The method according to any one of claims 1 to 4,
Wherein the concentration of the salt corresponds to a saturation concentration of the highest used carrier fluid. 5. The method according to any one of claims 1 to 4,
Wherein the concentration of the salt is less than 10% by weight based on the sizing composition. 7. The method according to any one of claims 1 to 6,
Characterized in that the carrier fluid comprises more than 50% by weight of water, preferably further comprising an alcohol comprising a polyalcohol and a polyether alcohol, in particular fully evaporable at 160 [deg.] C and 1013 mbar . 8. The method according to any one of claims 1 to 7,
Wherein the solids content of the sizing composition is 30 to 70 wt%. 9. The method according to any one of claims 1 to 8,
Wherein the sizing composition comprises 10 to 85% by weight of refractory material based on the solids content of the sizing composition. 10. The method according to any one of claims 1 to 9,
The refractory material may be selected from the group consisting of quartz, aluminum oxide, zirconium dioxide, aluminum silicate, zircon sand, zirconium silicate, olivine, talc, mica, coke, feldspar, diatomaceous earth, calcined kaolin, And / or a mixture thereof. 11. The method according to any one of claims 1 to 10,
Wherein the refractory material has a particle size of from 0.1 to 500 μm, especially from 1 to 200 μm, as measured by light scattering according to DIN / ISO 13320. 12. The method according to any one of claims 1 to 11,
By weight, based on the solids content of the sizing composition, of from 0.1 to 20% by weight, in particular from 0.5 to 5% by weight, of one or more binders. 13. The method according to any one of claims 1 to 12,
Characterized in that the sizing composition comprises from 0.1 to 10% by weight, in particular from 0.5 to 3% by weight, of a lustrous coal forming agent or graphite. A method of using a sizing composition according to any one of claims 1 to 13 for coating a mixture of mold materials, optionally diluted with water and then cured by water glass as binder. 15. The method of claim 14,
Characterized in that said molding material mixture comprises silicon dioxide, aluminum oxide, titanium oxide, zinc oxide and / or mixtures thereof, in particular amorphous silicon dioxide.